<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>

    <div id="app">
        <p>请选择你要购买的书籍</p>
        <ul>
            <li v-for="item in arr">{{ item.name }} <button @click="item.count++">买书</button></li>
        </ul>
        <table border="1" width="500" cellspacing="0">
            <tr>
                <th>序号</th>
                <th>书名</th>
                <th>单价</th>
                <th>数量</th>
                <th>合计</th>
            </tr>

            <tr v-for="(item, index) in arr">
                <td>{{ index + 1 }}</td>
                <td>{{ item.name }}</td>
                <td>{{ item.price }}</td>
                <td>{{ item.count }}</td>
                <td>{{ item.count * item.price }}</td>
            </tr>
        </table>
        <p>总价格为: {{ totalPrice }}</p>
    </div>

    <script src="./vue.js"></script>
    <script>
        new Vue({
            el: '#app',
            data: {
                arr: [
                    {
                        name: "水浒传",
                        price: 107,
                        count: 5,
                    },
                    {
                        name: "西游记",
                        price: 192,
                        count: 0,
                    },
                    {
                        name: "三国演义",
                        price: 219,
                        count: 0,
                    },
                    {
                        name: "红楼梦",
                        price: 178,
                        count: 0,
                    },
                ],

            },

            computed: {
                totalPrice () {
                    // 把数组中每一项的总价累加起来
                    // 每一项的总价就是单价*数量，再累加
                    return this.arr.reduce( (sum, v) => sum + v.price * v.count, 0)
                }
            }
        })

    </script>
</body>

</html>